Germany Patent Application 34 31 303, 1,6-naphthyridine derivatives with calcium antagonistic properties are described. (.+-.)-1,4-dihydro-5-isopropoxy-2-methyl-4-(2-trifluoromethylphenyl)-1,6-n aphthyridine-3-carboxylic acid [2-(N-methyl-N-phenylmethylamino)-ethyl] ester in the form of the hydrochloride is included. The corresponding U.S. Pat. Nos. are 4,711,901, 4,751,228, and 4,760,081, which are incorporated herein by reference.